Using ATC window de-activates zoom

Whenever I make a selection in the ATC window I lose the ability to zoom my view with +/- keys. The dirty solution is that I have to click on the screen before i can zoom again--often inconvenient because both hands are busy.

Is this an error? Is there anything I can do to prevent it from happening?

I have ATC window set to close as soon as I've made a selection.

In FSX I press the: ` key to close/open the ATC window that and fixes it, don't know if it will work in FS2004.

makes sense since ATC must be the last active window